feat(csharp): add csharp code for charper dynamic programming (#574)

* feat(csharp): add csharp code for charper dynamic programming

* add climbing_stairs_constraint_dp

codes/csharp/chapter_dynamic_programming/climbing_stairs_dfs.cs

@@ -0,0 +1,31 @@
+/**
+* File: climbing_stairs_dfs.cs
+* Created Time: 2023-06-30
+* Author: hpstory (hpstory1024@163.com)
+*/
+
+namespace hello_algo.chapter_dynamic_programming; 
+
+public class climbing_stairs_dfs {
+    /* 搜索 */
+    public int dfs(int i) {
+        // 已知 dp[1] 和 dp[2] ，返回之
+        if (i == 1 || i == 2)
+            return i;
+        // dp[i] = dp[i-1] + dp[i-2]
+        int count = dfs(i - 1) + dfs(i - 2);
+        return count;
+    }
+
+    /* 爬楼梯：搜索 */
+    public int climbingStairsDFS(int n) {
+        return dfs(n);
+    }
+
+    [Test]
+    public void Test() {
+        int n = 9;
+        int res = climbingStairsDFS(n);
+        Console.WriteLine($"爬 {n} 阶楼梯共有 {res} 种方案");
+    }
+}